Solve for $n$ : $-15 + n = -11$
Add $15$ to both sides: $ \begin{eqnarray} \\ -15 + n &=& -11 \\ \\ {+15} && {+15} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-15 + n} &\hphantom{=}& \hphantom{-11} \\ n &=& -11 {+ 15} \\ \end{eqnarray} $ Simplify. $ n = 4$